Lately, we’ve heard a lot about digital lockers for music as the next big thing in streaming media. Apple is rumored to be relaunching its MobileMe service next month with a digital locker for sharing media online and streaming it to mobile devices, and Google is also rumored to have a digital locker in the works. Now Amazon is reportedly working on a digital locker as well… and it could launch well before Apple and Google’s services.

According to sources speaking to CNet, Amazon is on the cup of unveiling a cloud-based storage system for music, video and ebook content that could be revealed as early as this week.

If you think about it, it makes sense that Amazon would be able to unveil a cloud based storage locker on the drop of a dime. After all, Amazon already keeps online backups of Kindle ebooks for users. In addition, Amazon’s S3 cluster of servers are already a staple of the cloud. In fact, Dropbox, one of the most popular cloud-based storage locker, already runs off of Amazon’s S3 cluster. Amazon also already has an excellent streaming architecture thanks to its Video On Demand service.

Given that the backend and infrastructure is already in place, it’s technically a piece of cake to enable a cloud-based storage locker for its users, beating the likes of Apple and Google to the punch. Less simple, however, are the various licensing issues at play… and rumor has it that Amazon’s launch is only being delayed at this point by the necessity of getting all the signatures on the contract.

This is interesting news, if true. You know, a lot of time, tech journalists write about the war between Apple and Google, but I think that’s going to start taking the back seat soon to the war between Apple and Amazon. Amazon’s already got its own media stores and its own App Store; now its getting its own cloud-based storage locker. Things are starting to heat up.